Sound actuated signal device for telephones



y 1950 H. c. ROWE SOUND ACTUATED SIGNAL DEVICE FOR TELEPHONES Filed May '5, 1947 Patented May 2, 195

EFF-ICE ,50 2% SOUND AGTUATED SIGNAL DEVI EF K TELEPHONES v Harry Cl Rowe, Ghi'cngo, pplication May- 3.1947, Serial no. 745,536

. Claims. (01.119 4) This invention. relates to sound actuat d si nal devices adapted to be used to indicate the existence of certain conditions-in a telephone circuit. More particularly it is a device which may be utilized, when a telephone oonversation'ha been temporarily discontinued without floreakinig'the connection, to give a suitable signal to one'of the parties who has le'ftthe telephone that the connected party is ready to resume the-conversation.

It is often necessary for one of the parties engaged in a telephone conversatlon to leave the phone temporarily. 'Thls normally means that even though no intelligence is being exchanged, the other partymust rema'inat the telephone and await the return of'the' nrstemention d Pa tycan be a great inconvenience ajs well as time consuming, which time could vbe'better.sp'ent in more productive activity.

Therefore, it would obviously be very desirable to havea device available which could be used incon'junc'tion with a telephone to automatically signal the return of the first-mentioned party to the telephone. The other party could then return to the telephone and theconversaiiion could be resumed. For various reasons it would be desirable "tofhave "the device so constructed that there no electrical-connection,nee'ded with the telephone withswhich is used. One or these the vund'esirab'flity'of ,having :to make any modification on already existing telephone-circuits which would 1;be tb'oth costly zand' "inconvenient, and perhaps *wouldnot be feasible {in many instances. Another is that it would bQeLde s'lrable to be abl eto utillzethe device with "any zone of several telephones merelybyiestalolishing the proper l hysical relationship betweenthat phone and the device, when the-phonejis itempora'rily .put .down. In other wordsgfan' auxiliary rack or cradle of some sort would have ;a natural utility, and it could be constructed 2519. part0! the device embodying the invention; sothat'the device would be put in an operative condition when a hand set is iplaced on that rack or dradle.

arrangement would allow theus'erof one such device -with any number .of separate itelenhflnes which are within reach ofithe device. since any of the hand sets could. be placed'on theme}; or BcradIeasdeSired.

[It is therefore an object of this {invention-J19 risrreadyto.resumetherconversationt 7 It is another object or this invention to 15rdvide a sound actuated signal device of the character described which is so constructed that no electrical connection with the telephone with which it is used is necessary, ,It is another object of this invention to provide a sound actuated signal device which maybe used with any number of telephones, so long as they are disposed so that the hand set may be phi sl cally coupled to the device.

it is still another Object of this invention to provide a sound actuated signal device which is of relatively simple design and which is economical to manufacture, to installand to operate.

"Still another object of this invention is -to provide a sound actuated signal device which n b adapted to give either a visual or auditorys'ignal', or 'both", if desired. I Further objects and a [vantages of this invention will becorne evident as the description'pro ceeds and from an examination of the accomanying -drawlng*which illustrates one embodiment of :the invention and in which similarnumerals refer to similar parts throughout the several views.

'In'the drawin EFiei a pers c vi of a dev e bo yineoneform Qf 'i -inv tie j is a perspective view of the device shown in Fig. *liwith-a.telephonelhand set in operative position on the device.

Fig. 3 is a circuit diagramof the embodiment of theint ntion shQw tin ig- Y-Re er'r ngnpw t fli s- '1 ni 'z. h nena flevi e;,; ene ailly sienaitedhy th -.nunie al t, ha a iront fac c mpr sin an aneu arl p sed s t o whi h is an extension of t ve ti a section 13- i ih an u a d sposition o these two fron ace se tions. wit xesnec tto 'eachother. a a s the. de ice .t irec te the telenh n ihand set 16 as is The tno uppo tin p sts I841: .011 th toenai s dis o edlnortion 11 .of the front f c are ,adap dt p t the receiver end 2 o h ihan set T henthe iatteris prope ly dispos d on he .ne a d ice as shown "Fig. 2. Iiikewise the two supportins 1 9. 1 5 ,122-ei n -the ver call d s o ed section ilzl 'o the f on ce o t dev e etad pted tosunport ithdmicmi hpneien 2e o ithe hand o:

it when thetlatteriis s 'di' h se Immediately alcove 121 8 .Sflpporliing posts ,ILB and tangent there o is .the .oircular section (.28 otresilienlt materialfrhem crq hone .is centinny-disposed in t is resilien -m te alaudits s exposed ria e fll is s bstantially .flush therewith.

as in Fig. 2. Therefore substantially no stray supporting posts i8l8 and adjacent the section- 28 of resilient material is adapted to be operated by the receiver end 28 of the hand set Is when it is disposed on the signal device as shown in Fig. 2. This disposition of the hand set and the resultant depression of the plunger of the switch member 26 normally puts the signal device in operative condition so that upon the return of the connected party to the telephone and a resumption of the conversation by him, the receiver end of the hand set will'be actuated and will cause sound vibrations to be transmitted directly to the microphone 30.

The signal device will then normally produce a signal to attract the attentions of the user, which may be in the form of the glowing of the signal light 80, or the sounding of a buzzer, or both. The operation of these will be more fully described below.

Referring now to Fig. 3, the schematic diagram of the signal device, the microphone 38 is shown connected to and adapted to be energized by a source of direct current which is here indicated as a battery 32. The microphone circuit includes the primary winding 34 of the transformer 36. Consequently any sound vibrations received by the microphone will be reproduced in the form of variations of the electrical current flowing through the primary winding 34. The secondary winding 38 of the transformer 36 is energized by these variations in the electrical current in the primary winding 34. The crystal rectifier 40',

together with the resistor 42, are connected to form a' closed circuit between the two ends of the secondary winding 38 and the condenser 44 is shunted across the resistor 42.

Electrically connected to this circuit between the crystal rectifier 48 and the resistor 42 is the contact point 46 of the relay'48. The relay arm 58 is connected to the control grid 52 of the thyraton tube 54 and the contact point 56 of the relay 48 is connected to the cathode 66 and .the screen grid 58. The movable arm 60 of the variable resistor 52 is connected to the end of the resistor 42 that is not connected to the crystal rectifier 40. The potentiometer 62 is connected across the source of electrical potential 64. The positive side of this source of electrical potential is connected to the cathode 66 of the tube 54 and also to one side of the plug 88 which is adapted to be plugged into a source of alternating line current. The opposite side of the plug 68 is connected to the contact point 18 of the switch member 26. The movable arm I2 of this switch member is connected to one end of the winding I4 of the relay 48. The opposite end of the winding 14 of the relay 48 is connected to the anode 16 of the tube 54. The resistor 1'8 and the glow discharge tube 80 are shunted in series 4 across th winding 14. The condenser 82 is also adapted to be shunted across the winding 14 by closing the manually operated switch 84. The transformer 86 is shown as a source of current for the heater 88 of the tube 54.

Although the sources of electrical potential 32 and 64 have both been shown in this schematic diagram as batteries, it should be understood that-a suitable power supply could be incorporatedin' the device to replace them. Also, no provision has been made for opening and closing the two circuits which include these two sources of electrical potential. It is contemplated that the switch member 28 might be used to close eitheror both of these circuits as well as the circuit connecting the plug 68 to the relay Winding- 14. A master switch 9!! can be used to contr01 t ;he,connection of the line current to the device, and the signal lamp 92 gives a visual indication when such connection is made.

When the device is to be used in the way described above the plug 68 is connected to a source of suitable alternating line voltage and the master switch 90 is closed. This energizes the transformer 8B which is the source of electrical energy for the'heater 88 of the tube 54 as shown in Fig. 3. The energizing of the heater 88 puts the tube 54 in operative condition. If the two sources of electrical potential 32 and 64 are also connected to their respective circuits, the signal device is' ready for actual operation. The movable arm 88 of the potentiometer 62 has been previously adjusted so that a suitable negative potential is applied to the control grid 52 of the tube 54 through the contact point 45 of the relay 48 which is normally in the position shown in Fig. 3. This negative potential is such that will prevent the firing of the tube 54 when the alternating line voltage is applied to the plate of the tube as will subsequently be described. The switch member 26 is normally in an open position, so that when the hand set is not on the device there is normally no potential applied to the plate 16 of the tube 54. a

' When it'is desired to use the device, after the connectedparty has left the telephone, the other party places the handset l6 on it in the manner shown in Fig. 2. Such disposition of the hand set I 6 causes the switch member 26 to close, which applies the'line voltage to the anode 16 through the relay winding 14, but the negative potential applied to the control grid 52 keeps the tube from fir The hand set is now in such a position that the microphone 38 and the circuit in which it is included will now be energized to any sound vibrations emanating from the, receiver end 28. When the voice frequencies from the receiver end of the hand set excite the microphone 38, the output of the transformer '36 is rectified by the crystal rectifier 48 which rectified current creates a potential drop across the resist0r'42 and a positive potential is therefore applied from the positive side'of the resistor42 to the grid 52, through the contact point 46 of the relay 48. This positive potential sufficiently overcomes the negative potential applied to the control grid 52 from the variable'resistance 62 through the movable arm 68, the resistor 42 and the contact point 46 of the relay 48, so that the tube 54 fires. The firing of the tube 54 closes the circuit from the source of'line voltage through the tube and the resulting anode current through the relay winding 14 immediately draws the relay arm 58 out of contact with thecontact'point 46 andinto contact with the Y contact poin t -56. When-the relay 4 arm 50 is so moved the controi grid 5i! "-is cdnnecteddirectlyto the cathode 55. This condition--continues as long as the anode -current' cpntinues to flow through the relay windin 14, which continues, in turn, as long as the tube re--- mains fired.

The line voltage applied from the plug 58 through the closed switch member 26 to the anode'lfi of the tube 54 has a significant effect on the'conelition of the tube; The alternatingcharacter of the line current causes the anode potential to swing from a very positive value to anequally negative value during each cycle as =long as switch member 26 is closed. When the anode potential reaches a value low enough to deionize the tube it stops conducting and the relay arm 50 immediately starts to return to the contact point 46. This occurs since the'current. flowing through the relay winding I4 is out off when the tube 54 stops conducting and since the arm 50 is normally urged toward contact point 46 when the relay is not energized.

Because of the relatively slow movement ofthe relay arm '50, the anode potential swings to a positive value sufificient to cause the tube to again fire, before the arm 50 reaches the contact point 46.-. The control grid 52.,is floating during the time that the relay arm 50 is moving away from;

the contact point, 56 and therefore has no appreciable influence on the effect of the cyclic variations of the potential of the anode 16. The relay arm is again pulled toward the contact point 56; when the tube fires. When it has again made contact with that point, the same cycle begins again. This will continue as long as switch member 26 remains closed, or in other words, until the hand set [6 is removed from the signal device l0. 7

The recurrent striking of the contact point 56 bythe, relay arm 50 produces sound vibrations which may be utilized as an audible signal to attract the attention of the party using the device, when the connected party resumes the conversation.

The glow discharge lamp shunted across the relay winding 14 also gives a visual indication when the tube is firing, since current will flow through the lamp and resistor 18 under such conditions, as well as through the relay winding 14. The buzzing of the relay 48 coupled with the glow of this lamp provides a very efiective signal for attracting the attention of the party using the device.

If it is desired to use the lamp 8D alone, without the buzzing of the relay 48, as a signaling means, the condenser 82 may be shunted across the relay winding 14 by closing the switch 84. When it is so connected in the circuit this condenser smooths out the pulsating direct current flowing through the relay winding when the tube 54 is conducting. This, in turn, establishes an average direct current level high enough to cause the relay arm 50 to be held continuously against contact point 56. The lamp 80 therefore glows as before but the buzzing signal is eliminated.

Once switch member 26 has been closed and the tube has been fired by the proper actuating vibrations created by the receiver of the hand set 16, the tube will continue to fire until switch member 26 is opened. Further vibrations created by this receiver will have no effect on the signal device, once it has started to produce a signal.

The negative potential normally applied to the control grid 52 from the potentiometer 62 may negative otential is. then appli o the cen r 3. beadiusted by setting the adjustable arm It is possible" to adjust this bias voltage so thatthe'tube will notbe fired except-by sounds-ar a; particular intensity, actuating the microphone"- 1 30; Becausestray sound vibrations, errand-om;

verticallyprojecting:rim which is adapted-to ens close the outer edges of the receiving 'endlll andx the microphone end 24 of thezhand set. These;

two projecting rims will then-act as baflles in preventing undesired sound vibrationsfromdeal'cf-s ing through sothat room noises. orthelike will? bemore. positively prevented 'from. actuating. either the microphone 30 or the microphone; end 24 of the hand set.

After thesignal device hasstarted to generate; asignal, it will continue to .doso until the switch; member. 26 is. opened by'removing; the-hand set,-. This opening of switch member .25 removes-the: alternately positive and negative;potential;from; theanode 76, so the, tube .54zimmediatelvs ps conducting. This, in turn:stops.;the fiowsoficur r rent through the relay vwindingr'l4,;so thatithe ree lay arm 5.6 is allo-wedto. return to its normah position and to make contact with point4li. The:

grid 52 as. discussed above and thewtubefil-w remain out: ofi until this bias. voltage is reduced; even though the line voltage; isapp-lied to=the anode 16, by closing switch member 25. The-de vice; may thereforereadily be. reset if accidentally" set off by; merely lifting the hand: set from they device to open switch member 26 long enoughto allow therelay arm 50 to return to 'the'normal'; position as described.

The drawing and the above discussion are not intended to represent the only possible form of this invention, in regard to details of construction. Changes in form and in the proportion of parts, as well as the substitution of equivalents are contemplated, as circumstances may suggest or render expedient, without departing from the spirit or scope of this invention.

What is claimed is:

1. A sound actuated signal device comprising a gas-filled rectifier tube having a cathode, an anode and a control electrode, means for coupling the anode-cathode circuit to a source of alternating current at will, a source of negative bias voltage for said control electrode of sumcient amplitude to normally prevent said tube from firing when said source of alternating current is connected to said anode-cathode circuit, a microphone. a source of direct current for energizing said microphone, a rectifying device coupled to said microphone circuit and poled to pass the positive pulses produced by activation of said microphone, resistance means in the rectifying device circuit, said control electrode being connected to the positive side of said resistance means so that when said microphone is sufliciently activated a positive voltage is impressed on said control electrode and said tube fires when said anode-cathode circuit is coupled to said source of alternating current, and solenoid controlled switch means normally connecting said some of bias voltage and the positive side of saidresistance means to said control electrode, said solenoid being in said anode-cathode circuit anddisposed so that said switch means disconnects said control electrode from said source of negative'bias voltage and said positive side of saidresistance means when said tube initially fires, and thereafter intermittently connects said control electrode to said cathode during each successive positive cycle of said alternating current until said anode-cathode circuit is disconnected;

from said source of alternating current.

2. A sound activated signal device adapted to be used with a telephone hand set comprising a housing adapted to support said hand set, a

microphone associated with said housing so thatthe receiver portion of said telephone hand set is in close association therewith when said hand set is supported by said housing, a gas filled rectifler tube having a cathode, an anode and a control electrode, means for coupling the anodecathode circuit to a source of alternating current at will, switch means in said anode-cathode cir cult adapted to be closed by said hand set when the latter is supported by said housing, a source of negative bias voltage normally connected to said control electrode, said bias voltage being of sufllcient amplitude to normally prevent said tube from firing when said source of alternating current is connected to said anode-cathode circuit, means for energizing said microphone, means for coupling the microphone circuit to said control electrode so that said microphone is adapted to impress a'positive counter voltage thereon when activated, said counter voltage being adapted to cause said tube to fire when of sufficient amplitude, and solenoid controlled switch means normally connecting said source of bias voltage and the source of counter voltage to said control electrode, said solenoid being in said anode-cathode circuit and disposed so that said last named switch means disconnects said control electrode from said sources when said tube initially fires and thereafter momentarily connects said control electrode to said cathode during each successive positive cycle of said alternating current until said first named switch means is opened. 7

3. A sound activated signal device of the char-- acter described in claim 2, further characterized in that said last named switch means comprises; a solenoid, an arm activated by said solenoid, and contact means on said arm adapted to creating audible sound when said arm is moved so that said control electrode is repeatedly connected to said cathode.

4. A sound activated signal device of the character described in claim 2, further comprising visual signal generating means in said anode-;

cathode circuit adapted to be energized when said tube fires.

5. A sound activated signal device of the chars acter described in claim 2, further comprising resistance means for adjusting the amount of negative bias voltage normally applied to said control electrode, so that the intensity of sound required to cause said tube to fire may be selectively adjusted.

HARRY C. ROWE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

